Electronic circuits for signaling



y 1950 w. BLISS 2,513,911

ELECTRONIC CIRCUITS FOR SIGNALING Original Filed June 22, 1944 4 Sheets-Sheet 1 RADIO T E LEG RAPH TRANSMITTER TONE KEYER NEH In, 2 Z 0 22 c 9 33m A ll- I w (I) Z A 0 5 w Z r! F.-

INVENTOR B WARREN H. BLISS.

o K/5 BY ATTORNEY July 4, 1950 STATION.

W. H. BLISS 4 ELECTRONIC CIRCUITS FOR SIGNALING Original Filed June 22, 1944 I Allllll 4 Sheets-Sheet 2 "I I I El Ann...

vHvIIv" RAD l O RECEIVER II I H Hull- FLYWHEEL OSCILLATOR INV WARREN H ENTOR BLI S.

ATTORNEY July 4, 1950 w. H. BLISS ,5

ELECTRONIC CIRCUITS FOR SIGNALING Original Filed June 22, 1944 4 Sheets-Sheet 3 WARREN H. BLI SS.

ATTORNEY July 4, 1950 w. H. BLISS ELECTRONIC CIRCUITS FOR SIGNALING Original Filed June 22, 1944 4 Sheets-Sheet 4 RECEIV1NG STATION RECORDER INVENTOR WARREN H. BLISS.

TELEGRAPH LOCKING CIRCUIT Patented July 4, 1950 UNITED s'mrss 2,513,911 ELECTRONIC CIRCUITS FOR SIGNALING Warren H. Bliss, Riverhe Radio Corporation of of Delaware ad, N. Y., assignor to America, a corporation 3 11 Claims.

This invention relates to electronic circuits for signaling. The instant application is a division of my co-pending application, Serial Number 541,569, which was filed June 22, 1944 and entitled Telegr'aph Secrecy System, now U. S. Patent 2,432,188 granted December 9, 1947.

In a secrecy system such as described in the parent application, of which this is a division, it has been found that when combining intelligence signals with signals from another source, useful for purposes of scrambling, certain advantages reside in the adoption of mixer circuits of the twin diode discharge tube type.

It is also found'that the dependability and efficiency of operation of a secrecy system such as disclosed in the parent application are insured by the adoption of certain trigger circuit technique such as is set forth in the instant applicatiofi.

Accordingly, it is an object of my invention to provide an improved signal mixer circuit such as may be used, for example, in carrying out the objects of the invention as stated in the copendin'g parent application.

from two difierent sources;

Fig. 2 shows a signal receiver including at least one trigger circuit which is found to be a useful component of a deciphering system;

Fig. 3 shows a plurality of graphs of signal wave forms delineated on a time scale, whereby the original code signals may be compared with the scrambled signals and with wave forms generated at the receiving station for unscrambling; and

Figs. 4, 5; and 6 illustrate respectively each of three alternative embodiments of the invention.

Fig. 1 shows the sending end equipment for a system using radio transmission. Unit 2 is a standard auto head for producing telegraph characters from perforated tape. It is driven by a synchronous motor from a 60-cycle supply. The output of this auto head is fed into a resizstor Ill and to one of the cathodes of dual diode l Commutator wheels 4 and 6 operate at the same speed and are also driven by a synchronous motor connected to the GO-cycle supply. Each wheel has a pick-up brush, and wheel 4 has one insulated and one conducting segment as shown, While wheel 6 has six insulated and six conducting segments. Each wheel has all its segments of equal length. For completing the circuits through these wheels the shaft of each is electrically connected to the plus terminal of battery 8 whose minus terminal is grounded. The brush 5 of wheel 4 and brush 1 of Wheel 6 are connected to resistor i l andthe second cathode of diode l2.

The anodes of diode l2 are connected to ground through series resistor I5 and battery I6 as shown. The upper end of resistor l 5 is connected to a tone keyer ll which is a conventional device for converting direct current pulses having mark (or space) significance into keyed tone signals. Item 18 is a conventional radio telegraph transmitter which radiates energy from antenna 19.

At the receiving terminal, Fig. 2, the signals are picked up by means of antenna 20 and radio receiver 2|. The output of the receiver taken as positive E. M. F. from its detector is fed through a biasing battery 22 to the control grid of a cathode output triode '23. The anode of triode 23 is directly connected to the positive plate supply while the output from cathode resistor 24 is connected to the cathode of a signal limiter diode 25. The anode of this diode is connected through resistor 26 and battery 2'! to ground as shown.

Triodes 30 and 35 comprise a flip-flop circuit having a single condition of stability. There are individual anode resistors 3i and 33 and a common cathode resistor 38. The control grid of triode 30 is fed through condenser 28 from the anode of diode 25 and is also connected to. the anode of tube 35 through resistor 32 and to ground through resistor 29. There is also a condenser 36 linking the anode of triode 30 to the control grid of triode 35. A resistor 3'! connects from the cathodes of the two triodes to the control grid of tube 35. I

The output ofthe above flipdlop circuit is connected through condenser 3d and resistor 10 to flywheel oscillator 40. This oscillator circuit is preferably the same as that described in United States Patent N 0. 2,274,841, issued to R. E. Mathes and W. H. Bliss, referring to Fig. l therein. Hence, it requires no detailed description herein. The output of this oscillator is supplied through a phase displacing circuit composed of inductance shown in graph 50.

3 41 and resistor 42 to the control grid of a gas tetrode 45.

Gas tetrodes 45 and are the essential parts of a second flip-flop circuit. There are anode resistors 43 and 53 with a cross-connecting commutating condenser 44. The cathode 'oftube 45 is connected'to ground through resistor 46 and condenser 41 in parallel and the screen grid is connected through resistor 48 and battery 49 in series to ground. This screen grid of tetrode 45 also receives the incoming signal'pulses from the anode of diode 25 through condenser 39. The control grid of tetrode 5| .is connected to ground through resistor 50 and to the anode of tube 45 through condenser 52. The cathode and screen grid of tube 5| are connected directly to ground.

A combining dual diode 55 has one anode connected to the anode of diode 25 and its other anode to the cathode of tetrode 45. The cathodes of diode 55 are both connected to .theccathode of diode 56 and to ground through a resistor 54. The anode of diode 56 is connected to a telegraph signal recorder 59 and to ground through series resistor 51 and battery 58. The telegraph recorder 59 maybe of the conventional ink slip type frequently used in the art.

Operation Waveform graph 60 of Fig. 3 shows the output of auto head 2 (Fig. 1) when the letters BL are to be transmitted. Graph Bl shows the output Waveform of E. M. F. at brush l of wheel-6 and graph 62 is the output of brush 5, wheel 4. It is essential that the wheels 4 and 5 and auto head 2 be so synchronized and phased that the outputs have relationships as shown by graphs 60, 6|, and 62. It is also necessary that the length of each segment on wheel 4 be an integral multiple of the unit length of the signals or an integral submultiple of the signal unit. ihe combination of the outputs of brushes 5 and I, produced by their parallel connection, is illustrated by graph'63.

Double diode l2 acts in a very specal way to combine the auto head output, graph 60, and the composite brush output, graph 63. Resistor l5 must be several times as large as resistors and II. With no output from the auto head 2 or brushes 5 and '1, the potential of point H is nearly that of ground potential, there being a small voltage drop through the diode l2 and resistors l0 and II. When a positive voltage from only one of the inputs (auto head or brushes) is applied to one of the cathodes of diode [2 this diode section cuts off and there is.

but a slight rise in potential at point ll because of the low resistance path through the other diode section. However, when positive voltages are applied simultaneously on the. two cathodes of diode l2 conduction through both halves of the tube is blocked and point II will rise to'and remain at the iull potentiol of battery Hi. It should be noted that the potentials of batteries 8 and 9 should be at least equal to that of battery l6.

For the example given in .Fig. 3 of transmitting the letters BL the combined output as observed by the potentialat point H is given by graph 64. This signal, which is similar to telegraph type material but which bears no apparent resemblance to the original message, is

The length of two succes sive segments on wheel 6 must'also be equal to transmitter. The secrecy of this system lies in the fact that the transmitted signal has a scrambled appearance and is unlike the original code characters. A close inspection of graphs 60 and 64 reveals that the secret message has been .derivedfrom the original :by :deleting certain small parts. These canbe supplied again at the receiving terminal.

At the receiving terminal the detector output of the radio receiver 2|, Fig. 2, is passed through triode 23 biased'beyond the cut-01f point to produce a noise threshold control and also passed through a diode 25 which acts as a peak limiter. At point 12 the recovered signal is essentially the same as that of graph 64 which was transmitted. v

This waveform is differentiated by condenser 28 and resistor 29 to give the trigger pulses shown by graph 65. These are applied to a flip-flop circuit composed of vacuum triodes 30 and 35. Tube is normally in a state of conduction and whenone of the positive trigger pulses (graph 65) from the anode of "diode 25 arrives at the controlgrid of triode '30, this "tube is flipped into "conduction "for a short period of time. Because of the regenerative action be tween these two tubes, only one ata time isconducting while the other is biased to cut-01f. Since tube 35 has no stable or fixed negative bias it always resumes conduction soon after tube 30 is triggererd. For the example shown the conduction period .for tube 30 should be about equal to one-half the baud length of the original signal.

Graph 66 shows the conduction vs. timerelation of tube '38 as derived from the wave form of graph 65. Graph .65 also shows the voltage variationat the anode of triode 35 and is fed into oscillator 40 to synchronize it as described in United States Patent 'No. 2,274,841 (previously mentioned). The output of this oscillator is displaced in phase by inductance 4| and resistor 42 and its waveform as observedacross resistor 42 is shown by graph T61.

Gas tetrodes 45 and 5! develop pulses to 'fill .'in those parts of the signal deleted at the sendingend. The'control grid .of'tetrode45 receives the .output from the oscillator (graph 61) and the screen grid of tetr0de-45has theincoming signal fromdiode 25 (graph 64) applied .to .it.

Tube 5| is normally conducting and tube 45- is triggered every time its control grid andscreen grid are simultaneously and momentarily .made sufficiently positive. A threshold line .13 .is shown in connection with graph GI to indicate on what part of the cycle tube 45 :willffire, provided that an incoming signalpotential is simultaneously applied to -the screen grid.

.Since tetrodes'45 and "Si are interconnected as a flip-flop circuit the conduction will always return backto tube 5| after an interval of time :determined by the values of condenser 52 .and

resistor The conduction vs. time character;-

istic for tetrode .45- is shown asgraph BBand this :is the output waveform of this tube as taken from its cathode.

"then-used to key a conventional radio telegraph r15 Double diode actstocombinethe incoming signal'from diode -25 .(graph54) Land the-filling in signal (graph :58) from tetrode 45. Inspection of graphs '54 and 158 show-.thatat some instants both signals are positive simultaneously and so a diode limiter 56 is used to level off the excess. The output voltage appears across resistor 51 and .isidenticalzwith the .original signal of :graph 60. .A telegraph recorder 59 may be used to register the received signal.

Fig. 4 illustrates a commutator wheel 95 which performs the combined functions of wheels 4 and 6 of Fig. 1. The output of this wheel 95, as picked up on brush 5, is as shown by graph 63, Fig. 3.

Fig. 5 illustrates an electronic system which performs the same function as commutator wheel I. A condenser 80 is slowly charged through series resistor 19 from the B+ plate supply. A as triode 18 with series cathode resistors 8| and 83 periodically discharges this condenser 8|] when its potential rises to a certain value. Cathode bypass condenser 82 maintains the cathode at an average positive potential which prevents a continuous discharge of condenser 80.

Each time condenser 89 is discharged a positive pulse will be developed across resistor 8|. This pulse will be passed on through condenser 84 to the control grid of gas triode 9|.

In order to properly synchronize the operation of the circuit of Fig. 5 with the standard auto head 2 and commutator wheel 4 a GO -cycle synchronizing voltage is fed into the control grid of triode 78 through condensers and 76. By adjustment of variable resistor 19 the frequency and synchronism of the pulses developed at the cathode of tube 78 are properly determined.

Gas triodes 9i and 92 comprise a flip-flop circuit with tube 92 being normally and stably conductive. Each pulse from triode 78 causes tube 9! to become conductive for a short interval of time but the state of conduction always returns to tube 92. Because of the above explained action awaveform like that illustrated by graph 6! Fig. 3, is developed at the cathode of triode 91. This output may be used in place of the output from commutator wheel 6.

A circuit identical with that of Fig. 5 may also be used in place of commutator wheel 4. In this case drive motor 3 would not be needed.

Fig. 6 illustrates a modification of the receiving station equipment which takes the place of the arrangement shown in Fig. 2. The receiving station here shown uses vacuum tubes I09 and H38 in place of the gas tetrodes 45 and 5| of Fig. 2. The oscillator unit 49 is the same in both embodiments. Other circuit components which are the same in Figs. 2 and 6 are given like reference numbers. Also for the sake of simplicity, certain portions of Fig. 2 are not shown in Fig. 6, even though they may be essential to the operation of thealternative embodiment.

The output of oscillator 40 causes triodes H16 and H18 to be alternatively conductive since this circuit is of the flip-flop type. The circuit connections for tubes I96 and H18 are conventional; including, as shown, anode resistors I92 and I93, grid resistors I09 and H2, a cathode resistor l H between ground and the cathode of tube I 09, and resistors I94 and M1 for cross coupling between the anode of one tube and the grid of the other tube. The output of this multivibrator circuit is taken from the cathode of tube I06 and is of the form shown by graph 6|, Fig. 3.

The operation of the circuit arrangement shown in Fig. 6 is further explained as follows: The incoming signal as shown by graph 64 in Fig. 3 develops anode potential variations at point 12 of Fig. 6. These anode potential variations are passed directly to the left-hand cathode in the twin diode tube 96 and also through capacitor 28 to control tube 39 as previously explained. The two diode sections of tube 96 in cooperation combinethe incoming signal with the output from tube I06 to produce a waveform representedby graph 14 in Fig. 3. This waveform is converted- States Patent No. 1,948,103, granted February 20 ,v

1934 to James L. Finch.

The space paths in both sections of tube 96 are rendered normally conductive by connecting a battery I09 and a resistor 99 in circuit between the anodes and ground. The cathode potentials are independently controllable by the potential drop in each of the two cathode resistors 91 and 98. Hence the resultant anode potential variations are reflected in variations of potential drop in resistor 99, the latter constituting aresistive coupling means for the locking circuit in I.

The output from the locking circuit ml is communicated to a telegraph recorder 59 in the same manner as indicated in Fig. 2. In other respects, the operation of the circuit arrangement of Fig. 6 will be readily understood in View of the-foregoing description.

Various other modifications of my invention may be made by those skilled in the 'art in view of the foregoing description, but will be understood to be comprehended within the scope of the invention as claimed.

I claim":

1. In a communication system, signal superimposing means including two independent sources of signals at least one of which constitutes message waves, means including a pair of rectifier electrode structures each including an anode and a cathode, a direct connection'between said anodes, individual cathode resistors directly connecting said cathodes to ground, a source of unidirectional potential, a direct current connection between the positive terminal of said source of unidirectional potential and said anodes through a common output resistor and its negative terminal connected to ground, circuit connections between each of said individual signal sources and a respective one of said cathodes, a keyer circuit coupled to said output resistor, and a transmitter controlled by said keyer circuit.

2. In a communication system, means for combining the effects of character signals derived zfrom two separate signal sources, at least one of which constitutes message waves, said means including a pair of normally conductive rectifier electrode structures each including an anode and a cathode, a direct connection between said anodes, individual cathode resistors directly connecting said cathodes to ground, a source of unidirectional potential, a direct current connection between the positive terminal of said source of unidirectional potential and said anodes through a common output resistor and a connection from the negative terminal of said source of potential to ground, connections between each of said signal sources and a respective one of said cathodes, and a utilization circuit coupled to said output resistor, whereby the simultaneous application of signals to said cathodes when of positive polarity causes said rectifier electrode structures to cease conduction and hence to afiect said utilization circuit.

3. In a pulse communication system, means for converting message waves in the form of code character signals into shorter duration pulse signals, said means including a pair of, rectifiers each including an anode and a cathode, a direct connection between said anodes, individual oath-i ode resistors connecting said cathodes to ground, a source of unidirectional potential having its positive terminal connected to said anodes through a common output resistor and its negative terminal connected to ground, a source of said code character intelligence signals connected to the cathode end of one of said cathodelresistors, a source of periodically repeating pulses of shorter duration connected to the cathode end of said other cathode resistor, and .a utilization circuit coupled to said output. resistor.

4, In a pulse communication system, means for converting message waves in the form of code character signals into shorter duration pulse. signals, said means including a pair of rectifierseach including an anode and a cathode, a direct connection between said anodes, individual cathode resistors connecting said cathodes to ground, a source of unidirectional potential havin its positive terminal connected to said anodes through a common output resistor and its negative terminal connected to ground, a source of code character intelligence signals of positive polarity connected to the cathode end of one ofsaid cathode resistors, a source of periodically repeat ing pulses of positive polarity of shorter duration connected to the cathode end of said other cathode resistor, and a utilization circuit coupled to said output resistor, whereby the'si'multaneous application of the positive polarity sig nals and pulses to said cathodes causes said rectifiers .to cease conductionat the same time for. the duration of said shorter duration pulses, and hence a momentary rise in potential on, said. anodes of sufficient magnitude to affect said utilization circuit.

5. In a pulse communication system, means for converting message waves in the form of recurring spaced unidirectional pulses. into. shorter duration pulses, said means including a pair of: rectifiers including an. output electrode and an input electrode, individual impedances respectively coupling the input electrodes of said rectifiers directly to a point of reference potential, 2. common output circuit for said rectifiers including a source of unidirectional potential having its positive terminal connected to said output electrodes and its. negative terminal directly connected to said pointof reference potential, a source of recurring spaced unidirectional pulses connected to the input electrode of one rectifier, a source of periodically repeatingpulsesof shorter duration than said recurring pulses but .01 the same polarity as said pulses connected to the input electrode of said other rectifier, and a utilization circuit coupled to said common output circuit. 1

'6. In a pulse comrnunication system, means for converting recurring spaced unidirectional pulses into shorter duration @pulses, said means including apair of rectifiers including an output electrode and an input electrode, a common output circuit for said .recitifiers including .a direct connection between said output electrodes and a source of unidirectional potential having its positive terminal connected; to said output electrodes, a source of message waves in the form of recurring spaced unidirectional pulses of positive polarity connected tothe input electrode of one rectifier, a source of periodically repeating pulses of shorter duration than said recurring pulses but of the same polarity as saidsignals connected to the input electrode of said other rectifier, and a, utilization circuit coupled to said common output circuit, whereby the simultaneous application of the positive polarity pulses from both said sources to said input electrodes, causes said rectifiers to cease. conduction at, the same time for the .duration .oi'saidshorter dura-.- tion pulses as a result. of which there is a rise in potential on said output electrodes of suflicient, magnitude to affect said utilization circuit for the duration of said shortcrdur-ation pulses.

'7. In a pulse communication system, a gate arrangement comprising a pair of rectifiers each including an anode and a cathode, a direct connection between said anodes, individual cathode resistors directly connecting said cathodes to ground, a source of anode polarizing potential connected to said anodes through a. common output resistor, a source of ,message waves in. the form of signal intelligence pulses connected: to the cathode of one of said rectifiers and a source of periodically repeating pulses connected to the cathode of the other rectifier, and a utilization circuit coupled to said output resistor.

.8. In a pulse communication system, a gate arrangement comprising a pair of rectifiers each including an anode and a cathode, a direct connection between said anodes, individual cathode resistors directly connecting said cathodes. to ground, a source of anode polarizing potential connected to said anodes through a common output resistor, a source of message waves'in the form of signal intelligence pulses of positive p0- larity connected to the cathode of one of said rectifiers and a source of periodically repeating pulses of positive polarity connected to the oathode of the other rectifier, and a utilization circuit coupled to said output. resistor, whereby the simultaneous application of the positive polarity pulses to said cathode causes said rectifiers. to cease conduction at the same time, as a result of which there is a rise in potential across said output resistor of sufiicientmagnitude to affect said utilization circuit.

9. In a pulse communication system, means for converting code character intelligence signals into shorter duration pulse signals, said means including a pair of rectifiers each including an anode and a cathode, a direct connection between one electrode of one rectifier and a corresponding electrode of the other rectifier, individual'resistors directly connecting the other said electrodes of said rectifiers to ground, a source of; unidirectional potential having one of its terminals connected to said direct connection through a common output resistor and its other terminal connected to ground, a source of message waves in the form of code chara ter intelligence signals connected to the electrode end of one of said individual resistors, a source of periodically repeating pulses of shorter duration connected to the electrode end of the other individual resistor, and a utilization circuit coupled to said output resistor.

10. In a pulse communication system, means for converting pulse intelligence signals into shorter duration pulse signals, said means including a pair of rectifiers each, including an anode and a cathode, a direct connection between one electrode of one rectifier and a corresponding electrode of the other rectifier, individual resistors directly connecting the other said electrodes of said rectifiers to ground, a source of unidirectional potential having one of its terminals connected to said direct connection through a common output resistor and its, other terminal connected to ground, a source oimessage waves in the form of pulse intelligencesignals connected to the electrode end of one of said individual resistors, a source of periodically repeating waves of shorter duration connected to the electrode end of the other individual resistor, and a utilization circuit coupled to said output resistor.

11. In a communication system, a combining circuit for causing two separate trains of signal pulses to be superimposed in a single output circuit, comprising a twin diode discharge device having its anodes connected through a common load resistor to the positive terminal of a direct current source the negative terminal of which is grounded, two cathode resistors each connected between a respective cathode and ground, and independent keying means each arranged to apply signal pulses of positive polarity directly to a respective one of said cathodes, thereby to cut ofi emission therefrom, one of said keying means being controlled by a source of message waves the ohmic value of said common load resistor being large relative to that of said cathode resistors,

WARREN H. BLISS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,381,155 Frommer Aug. 7, 1945 2,400,133 Pray May 14, 1946 2,403,918 Grosdofl July 16, 1946 2,408,078 Labin et a1 Sept. 24, 1946 2,411,062 Schade Nov. 12, 1946 

